Extraction of blood pool in dynamic O-15 water PET with slow-infusion using factor analysis

Accurate measurement of myocardial blood flow (MBF) can be achieved noninvasively by using dynamic PET with a slow-infusion of O-15 water incorporating O-15 CO gas scan, which is used for identification of myocardium regions to obtain an accurate input function. Although there have been studies using PET with bolus-injection, the applicability of factor analysis (FA) to slow-infused water data has not been examined yet. In this study, we investigated a method for extracting blood pool activities from dynamic water image with slow-infusion using FA. A dynamic PET scan was performed with slow-infusion of water, after a static CO scan. Both components of blood pool and myocardial tissue were separated from the acquired dynamic water image using FA. Time-activity curve (TAC) of blood pool and myocardium were extracted, and the images of blood volume (VB) and extravascular tissue density (Dev) were generated, respectively. The TAC shape of blood pool was agreed to that of true input function. The effect of spillover from blood pool to myocardium was dramatically eliminated in TAC shape. The both images of VB and myocardium by FA were similar with VB image by CO and washout-phase image of dynamic data, respectively. Both Dev image by CO image and FA were also comparable in terms of spatial distribution and count scale. This approach incorporating factor analysis could be useful for improved quantitation of MBF using simplified acquisition protocol without CO scan.